This application claims the priority of German Patent No. 197 30 563.6, filed Jul. 17, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to the use of a holographic video screen as a display surface in a vehicle, as well as to a display system in a vehicle.
The vehicle category includes, for example, motor vehicles, trains, special vehicles, airplanes and ships. Various embodiments have become known as display units and display video screens (displays) for use in motor vehicles. It is known, for example, to provide mechanical indicator instruments which may be constructed as an instrument cluster and display various information (for example, vehicle speed, covered distance, time of day, rotational engine speed and optionally additional quantities). Furthermore, it is known to construct displays as LCD video screens. It has also been suggested to provide a holographic display in the windshield area. In the case of this latter application, it is advantageous that the virtual image display can be applied to a distance such that, relative to the distance of the display with respect to the distance of the observed traffic situation, no adjustment of the driver""s vision is required.
German patent documents 197 00 162.9 and 197 03 592.2, which are not prior art, disclose the provision of a holographic video screen for a laser front projection and a laser rear projection. In normal ambient light, this video screen is black. However, for certain wavelengths of the light, this video screen can be constructed such that this light is transmitted and reflected at a certain fixed angle. According to these references, this screen does not require a plane construction. On the contrary, it is possible to construct this video screen with an almost arbitrary surface contour. For details relative to the video screen, the disclosures of the above-referenced German patent documents are expressly incorporated by reference herein.
From non prior art reference, Veligdan, James T. xe2x80x9cUnique Interactive Projection Display Screen.xe2x80x9d Brookhaven National Laboratory, Upton, N.Y., systems utilizing Sheimpflug type optics are known. For details regarding such Sheimpflug type optical devices, the disclosure of the above-referenced document is expressly incorporated by reference herein.
In the holographic video screen according to the invention, the contrast of the screen is significantly improved because the ambient light is absorbed by the video screen. It is significantly easier for the driver to recognize the display of vehicle-specific or driving-situation-specific quantities, such as, for example, a holographic display of the speedometer. Furthermore, in comparison to conventional display units, space requirements are considerably reduced. In contrast to other display units, the amount of current required is reduced. This reduction leads to an increase in the contrast performance of the screen. As a result, it becomes possible to reduce the video screen brightness by the black background.
In contrast to conventional light generation, when laser beams are used for generating the images, a further considerable reduction of the required current is possible. This is because no infrared light and therefore no corresponding heat radiation is generated. The power consumption is typically from 1.25% (LCD projection) to 10% (CRT projection) in comparison to conventional systems. This is advantageous, for example, with respect to the charging balance of the battery.
The driver""s viewing angle with respect to the screen can be almost arbitrarily defined. With respect to its surface design, the video screen is flexible. As a result, sharp edges can be avoided. This has an advantageous effect with respect to passive safety in the event of a crash. In addition, the surface of the video screen is flexible with respect to its dimension and shape. An emission of the image information of the holographic video screen takes place in an angular area, which is defined and adjustable during the generation of the hologram of a video screen (preferably toward the viewer). This has the result of preventing undesirable reflections, for example, in the windshield. Since external light through the windshield logically radiates from a different direction on the surface than the projection system and the color of the light also deviates from the color of the light of the projection system, the external light does not interfere with the actual image information. For this reason, no special shading (for example, hoods or scoops) is required which saves cost and space and results in more design freedom.
According to advantageous embodiments of the invention, the video screen is black, or preferably of a dark color in order to achieve a good contrast. According to design-related requirements, the video screen can also be constructed in gray, or of another color.
In another embodiment of the present invention, the video screen operates in a direct front projection system. In another embodiment according to the invention, the video screen operates in a transmitted-light projection system. Using these two advantageous projection embodiments, it is possible to mount the projection system corresponding to the available installation space in the motor vehicle. Thus, for example, the projection system can be constructed on the driver""s side as a transmitted-light projection. This is because, in comparison to the previous speedometers, installation space is saved behind the dashboard. On the front passenger side, the projection system may, under certain circumstances, be constructed as a projection system utilizing direct front projection because the available space behind the dashboard is limited due to the presence of the air bag and the glove compartment.
In yet another embodiment of the present invention, the video screen is constructed such that its surface is soft. As a result, the passive safety of the vehicle can be taken into account if possible surfaces, on which a vehicle occupant may impact in the event of an accident, are constructed in a correspondingly soft manner.
In still another embodiment of the invention, the video screen is arranged in the driver""s viewing area below the windshield. Advantageously, such a video screen can be used instead of previously used dashboard inserts behind the steering wheel. Using a projection system, the corresponding information can be displayed to the vehicle driver.
In another embodiment of the invention, the video screen is arranged in the viewing area of the front passenger below the windshield. Because of its location, the video screen can be easily assigned to the front passenger.
In even another embodiment of the invention, the video screen is at least essentially mounted on the covering of an air bag. In this case, it is advantageous that the covering of the air bag cannot be used as an area to deposit objects because these may disturb the air bag in the event of the air bag triggering during an accident. Since the covering of the air bag is therefore always free of objects, an undisturbed display of an image is also possible.
In a further embodiment of the invention, the video screen is essentially mounted on the cover of the glove compartment. Since the cover of the glove compartment can not be used as a surface upon which objects are placed and is also arranged within the grasp of the front passenger, this cover is also suitable for use as a surface of the video screen.
In still another embodiment of the invention, the video screen is arranged in at least one of the two lateral surfaces of the center dome of the vehicle. This provides good overall visibility for the driver and the front passenger.
In a further embodiment of the invention, the video screen is arranged on the surface of the center dome. As a result of this arrangement, in cases of a corresponding fixed angle, the video screen can be seen by all vehicle occupants.
In yet another embodiment of the invention, the video screen is arranged on a slightly bent surface of the ceiling (in the center area of the forward area of the vehicle). Here, the video screen can (for example) be irradiated by at least one projection system which is arranged in the rearward area of the vehicle. The video screens are then highly visible at correspondingly adjusted fixed viewing angles by the rear occupants of the vehicle.
In another embodiment of the present invention, an illumination device is situated behind the slightly bent surface of the ceiling. As a result of positioning the illumination device behind the surface, the space formed is utilized. Moreover, the projection of the illumination device may advantageously be in the direction of the rear occupants"" knee areas and may optionally be rotatable.
In an even further embodiment of the invention, the video screen may be mounted behind and/or on the interior side of a sun visor. This results in an optimal utilization of the space.
In yet another embodiment of the current invention, the video screen is mounted on the rear surface of the headrests of the front seats. This allows the rear occupants to see the video screen without turning their heads. Here, the usable video screen surface can correspond to the overall size of the headrest and, with respect to its external shape, may be adapted to the contour of the headrest.
In still another embodiment of the invention, the video screen is larger than the projection surface on the video screen. As a result, no readjustment of the projection system""s projection onto the video screen is required when the front seat is adjusted.
According to another embodiment of the invention, a change of the direction of the projection system takes place with an adjustment of the front seat and/or of the headrest of the front seat. This advantageously adapts the projection direction of the projected image when the front seats are adjusted to an optimum direction.
In another embodiment of the invention, the video screen is used as part of a display system of a motor vehicle. In addition to the video screen 3, the display system has at least two projection systems. Here, the images of the two projection systems are visible from the same viewing angle. As a result, for example, mutually overlapping images can be displayed. It is also possible to display a speedometer, where a first image represents the scaling of the speedometer. Another image may display the indicator position corresponding to the momentary speed. This enables the display of a speedometer by superimposing the two images.
In a further embodiment of the present invention, the projection systems have different colors. This results, for example, in better recognition of the indicator position.
In yet a further embodiment of the present invention, the video screen is used as part of a display system of the motor vehicle. Here, the display system has at least two projection systems in addition to the video screen. In the present embodiment, the images of the two projection systems are visible from different viewing angles. As a result, via a video screen, different images can be displayed for several occupants of the vehicle. Vehicle-specific, driving-condition-specific and driving-situation specific data can, for example, be displayed to the vehicle driver, while other information, such as a video or tourist-type information concerning the region through which the automobile is driving, can be displayed to the other vehicle occupants.
In still another embodiment of the invention, at least two projection systems exist for the at least one video screen. The images of the projection systems can be seen from different viewing angles. This, in essence, is an advantageous combination of several of the inventive embodiments.
In correspondence with the indicated uses, the video screens can be arranged such that undesirable reflections are avoided, because the video screen principle and other light influences have no contrast-reducing effect on the screen.